This invention relates to medical implants for improving or modifying the performance of tissue structures in a patient's body such as a sphincter, a tubular conduit, or an organ. An illustrative use of the invention is improving the performance of a patient's lower esophageal sphincter (“LES”) as a treatment for gastro-esophageal reflux disorder or disease (“GERD”). However, this is only an example of how the invention may be used, and many other uses will be readily apparent to those skilled in the art. To list just a few further examples, the invention may be applied to other sphincters in the body such as sphincters in the urinary tract and elsewhere in the digestive tract. The apparatus of the invention may be used around the stomach as part of a treatment for obesity.
A common cause of GERD is inadequate functioning of the LES. The LES (and perhaps some associated tissue structures) normally keeps the lower part of the esophagus closed in order to prevent stomach contents from entering the esophagus. The LES opens during swallowing to allow whatever is being swallowed to pass from the esophagus into the stomach. The LES also opens to allow excess pressure in the stomach to escape via the esophagus. However, normal stomach pressure is substantially resisted by a normally functioning LES to keep the contents of the stomach from entering the esophagus. In a patient with GERD the cause is frequently an LES that has lost its ability (strength or “tone”) to resist normal stomach pressure and prevent stomach contents from coming back into the esophagus. This can cause discomfort (“heartburn”), and if left untreated, can cause damage to the esophagus that can lead to very serious adverse consequences for the patient.
It has been proposed to implant magnets in a GERD patient to improve the strength or tone of the patient's LES. For example, two magnets may be implanted in the esophagus on respective opposite sides of the esophageal lumen at or near the LES. Magnetic attraction between the magnets helps to hold the esophagus closed (except during swallowing or excess stomach pressure venting) and thereby reduces or eliminates the reflux of GERD. In following this approach, it would be desirable to avoid subjecting tissue to long-term, direct pressure from the magnets, such as when tissue between two mutually attracting magnets or magnetic structures is the only thing keeping the magnets or magnetic structures apart. Such pressure can interfere with blood flow to the tissue between the magnets or magnetic structures, which can be unhealthy for that tissue. For example, tissue death (necrosis) can result.